The present invention relates to apparatus for use in the mining industry and more particularly to equipment for accurately determining whether the angle of inclination of a explosive bore hole is being drilled within predeteremined parimeters. In the mining industry, conventional mining techniques include the placement of an explosive charge within the solid material in order to break loose a portion of the mined material. Typically, the explosive is placed in a series of bore holes which are precisely drilled. Since water is typically used to wash out the holes during the drilling process, the holes must be drilled at an incline to insure drainage of the water. However, if the angle at which the holes are drilled is not uniform and readily determinable, the overall effectiveness of the blast will be significantly affected. Further, if the angle of inclination is too steep, the bore hole would penetrate the roof of the mine shaft, potentially causing a very serious safety condition. Thus there is a need for a device which is accurate, essentially maintenance free, easy and simple to operate, adapted to operate in a high vibration and debris filled environment, to constantly and continuously monitor the angle of inclination at which the hole is being drilled and communicate this information to the drill operator.